are sometimes encountered In laboratory and theoretical work. Commonly used 

 wave height parameters in each of the three classes are listed in Table 3-1. 



TABLE 3-1. Classes of commonly used wave height parameters. 



Wave height parameters within each class are clearly and easily inter- 

 related. However, confusion can arise when parameters from different classes 

 must be related. The primary source of confusion is the fundamental 

 differences in the definition bases. Efforts to specify the relationship 

 between parameters in different classes are further complicated by a 

 dependence on water depth and wave characteristics such as steepness. For 

 example, the relationship between the height of a wave and the potential 

 energy contained in the deformed water surface changes as the wave profile 

 changes shape in shallow water. Wave profiles computed by the stream-function 

 theory (Chapter 2, Section II, h; Dean, 1974) for 40 cases clearly illustrate 

 the dramatic differences induced by high wave steepness and shallow water 

 (Fig. 3-7). These differences should be recognized by coastal engineers 

 dealing with breaking or near-breaking wave conditions. 



Dean's (1974) computations provide an approximate means of relating 

 statistical-based with energy-based wave parameters. Although Dean's 

 computations represent uniform waves propagating over a flat bottom, they can 

 be expected to provide useful insight on how the ratio of wave height to the 

 standard deviation of the wave profile can vary with water depth and wave 

 steepness (Fig. 3-8). H^ is a combined depth-limited and steepness-limited 

 breaking wave height that can be estimated as a function of H/gT'^ and d/gT^ 

 by the breaking limit curve in Figure 2-7 in Chapter 2. To aid in estimating 



a realistic practical limit on the ratio H /H for real ocean waves, the 



'^ s m 



upper envelope of estimates from two comprehensive field experiments in which 

 wave measurements were collected along a shore-perpendicular line of gages 

 extending through and beyond the surf zone is also shown. The figure 



indicates that 



H is approximately equal to 



H 



in deep water , but can be 



s "^ •^ •* ' m 

 at least 30 percent greater in shallow water for breaking waves. Thus, it is 



important to distinguish between 

 waves. 



and H for depth-limited breaking 



m 



Since monochromatic waves are actually a different phenomenon than 

 irregular waves with the most satisfactory way to relate monochromatic-based 



3-15 



